Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology

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pISSN 2288-0585 eISSN 2288-6850

Evaluation of a Modified Scheme for the Species Identification of Enterococci

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2002 December Volume 5, Issue 2, pages 129-136.

Evaluation of a Modified Scheme for the Species Identification of Enterococci

Myungsook Kim*,** Sunhee Kim* Giyeon Kang,* Dongeun Yong*,**, Kyungwon Lee*,**, Yunsop Chong,*,** and Shin Moo Kim***

Department of Laboratory Medicine,* Research Institute of Bacterial Resistance,** Yonsei University College of Medicine, Seoul; Department of Clinical Pathology, Wonkwang Health Science College, Iksan, Chonbuk, Korea

Abstract

Background: Rapid species identification of enterococci is necessary for optimal treatment of infected patients as they are frequently resistant to various antimicrobial agents. Minimal identification scheme is necessary to cut the laboratory cost. In this study, a minimal identification system was modified to expand the identifiable species.

Methods:Performance of MGP test was compared to that of MIO motility test. Colonies on blood agar were used to inoculate primary identification media: SFA, BEAA, mannitol agar, tellurite agar, sorbose agar and MGP agar, which were prepared in biplates. Pigment production was tested when necessary using colonies on a blood agar. Isolates, which were not identifiable by the primary test, were inoculated to secondary test media: ADH, and arabinose-, raffinose- and sucrose-containing CTA. Vitek GPI cards were used to test isolates with a doubtful identification or no identification.

Results:MGP test was selected for the modified scheme, as it was more rapid and accurate than motility test. Among the 879 clinical isolates of enterococci, 462 (52.6%) and 3 (0.3%) were identified as E. faecalis and E. casseliflavus, respectively, by the primary test only. With the additional secondary tests, 379 (43.1%) isolates were identified as E. faecium. Vitek test showed the identification of 4 isolates with atypical test results and 5 isolates of rare species by modified scheme were correct. Nine isolates (1.0 %) were not identifiable by the modified scheme.

Conclusions: The modified minimal identification scheme which included MGP test identified most E. faecalis isolates rapidly and accurately. Most of E. faecium isolates were identified with the additional secondary tests. In conclusion, the system is useful for the identification of commonly isolated species of enterococci. (Korean J Clin Microbiol 2002;5:129-136)

Keywords

pecies identification, Enterococci, Modified scheme